1. Field of the Invention
The present invention relates to an adjustable overhead rocker cam valve operating device for an internal combustion engine and, in particular, to a device for use with racecars or high performance automobiles.
2. Description of the Prior Art
Prior valve control systems utilized fixed rocker arms which require considerable movement, or multiple rocker arm elements which are engageable with different cam profiles and means to interconnect the different rocker arm elements. An example is the system described in U.S. Pat. No. 5,623,897, issued Apr. 29, 1997. Other systems utilize a plurality of rocker arms positioned adjacent to one another, and a plurality of valve operating cams. Such a system is described in U.S. Pat. No. 5,979,379, issued Nov. 9, 1999. The overhead rocker cam valve operating device of application Ser. No. 09/565,001, now U.S. Pat. No. 6,273,040, provides a system which can be adjusted for more or less power, namely can be adjusted to a performance mode or an economy mode. However, this system requires a link in engagement with the cam arm, the link being affixed to the engine head or block.
In accordance with the principle of the present invention, there is provided an overhead rocker cam system which is adjustable and minimizes valve train movement. The system provides geometric advantages such that the rocker arm does not move away from the valve stem in an excessive manner. The rocker cam is adjustable so that the farther away the connecting pin is moved from the rocker cam, the less extra lift is provided. Thus, the rocker cam and connecting pin can be adjusted for more or less power or, with a performance type automobile, can be adjusted to a performance mode or an economy mode.
In particular, this invention provides fixed side plates, the rocker cam positioned there between, whereby the link of the prior invention, in engagement with the cam arm and affixed to the engine head, is no longer required. The side plates include a slot for receiving the pin in the cam arm to provide for suitable adjustment of the cam system. In addition to eliminating the need for a link in engagement with the cam arm and affixed to the engine head, the system provides a xe2x80x9csquarexe2x80x9d profile of the lift versus duration curve, providing more power.